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Cav
Cav
Visitor III
March 13, 2025
Question

Google reCAPTCHA - Allow access from a DMZ server

  • March 13, 2025
  • 2 replies
  • 1401 views

Hi, I am after some guidance on anyone who has setup a DMZ Server to utilise Google re-CAPTCHA.   The DMZ area is restricted for outbound Internet access and any server that requires a service is locked down to only what it needs.

 

What is the best action to allow a DMZ server to Google re-CAPTCHA on a Fortigate 600F Firewall?

 

Info.  Google apparently uses 

https://www.google.com/recaptcha/api/siteverify   &  https://www.google.com/recaptcha/api.js 

DNS to resolve to google.com

 

The odd guide recommends allowing access to the following subnets but this equates to around 212,992 IP Addresses.

The reCAPTCHA servers can be located on any IP address owned by Google. While we can not provide official support for IP Address-based ACLs, Google's public IP space can be found by issuing the following command from a Linux/Unix box:

dig -t TXT _netblocks.google.com

The result right now is:

ip4:216.239.32.0/19 ip4:64.233.160.0/19 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:209.85.128.0/17 ip4:66.102.0.0/20 ip4:74.125.0.0/16 ip4:64.18.0.0/20 ip4:207.126.144.0/20 ip4:173.194.0.0/16

 

 The Fortigate doesn't have a predefined Internet Service for Google re-CAPTCHA so is there a way of restricting this any further or will it need allowing the vast IP range?

 

Is there a way to allow the full URL's for the Captcha as the entire url is not a FQDN?

 

Thoughts & Help would be appreciated.

 

 

2 replies

Stephen_G
Moderator
Stephen_G
Moderator
March 16, 2025

Hello,


Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.


Thanks,

Stephen_G - Fortinet Community Team
    Cav
    CavAuthor
    Visitor III
    March 18, 2025

    Hi, after looking into this I have tried to implement a customized Web Filter.  The filter contains the URL filter to sepcify the URL's and then a global * wildcard block at then end.  This is then applied to the Policy rulebase.  The rule is set to allow the server to external(www) with 'any'.  The rule then is controled by the web custom filter.   This looks promising now and will update the post if this works fine and the alternative option.   I can send screenshots for anyone having this issue if needed.

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